1. Field of the Invention
The present invention relates to an image processing apparatus and image processing method, and particularly relates to an image processing apparatus and image processing method that are able to convert the resolution of an inputted image from low resolution to high resolution, and output the resulting image.
2. Description of the Related Art
When printing an image, which was acquired from a scanning device such as a scanner at low resolution, at high resolution, it is necessary to convert the resolution of the image from low resolution to high resolution. Moreover, when transferring an image over a network at low resolution in order to reduce the network load, and then displaying or printing that image at high resolution, it is necessary to perform resolution conversion in order to convert the image from low resolution to high resolution.
In the past, many methods have been proposed as methods for converting the resolution of an image that was inputted at low resolution to high resolution. As an interpolation method that is often used when performing resolution conversion on a multi-gradation image, there is a nearest neighbor interpolation method that sets the signal value of the nearest dot from the interpolation point for which interpolation is to be performed as is as the signal value for the interpolation point. Moreover, there is a bi-linear interpolation method that sets the signal value of the interpolation point by a linear equation based on the signal value of a 2×2 pixel (4-pixel) dot around the interpolation point. Furthermore, there is a bi-cubic interpolation method that sets the signal value for the interpolation point by using a cubic polynomial equation from 4×4 pixels (16 pixels) around the interpolation point.